In the course of the repeated production of diagnostic images, for example in connection with X-ray photography, computer tomography, magnetic resistance tomography, ultrasound tomography or positron-emitting tomography, but also in connection with therapeutic, in particular radiation-therapeutic systems, it is necessary to achieve a positioning of the patient in a repeated procedure, which is as accurate as possible in relation to the coordinate system of the respective system for checking the ongoing process, or for the optimal treatment of the respective area of the body.
In this connection, it is known to apply markings to the patient, which are compared with reference points in the system, wherein the patient and the system can be displaced in such a way that these markings are each brought into congruence with a reference system of the device. Reference is made to the Laid-Open, Non-Examined Patent Application DE-OS 44 32 890 and to U.S. Pat. No. 6,279,579 in regard to such a system and such a method.
The problem with these known methods and devices lies in that in case of repeated treatments, the respective markings must be reapplied to the patient, since it is actually not possible to provide the patient with permanent markings or visible lesions which remain unchanged over a long period of time.
The reapplication of such markings is prone to errors which in actual use result in that repositioning of the patients is located within a range of 5 to 8 mm of reproduction accuracy, with occasionally greater deviations of up to 10 mm.